<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>animation-duration</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }
    body {
      width: 100vw;
      height: 100vh;
      /* background: #34495e; */
      display: grid;
      grid-template-rows: 10vh 1fr 10vh;
    }
    header {
      background: #e67e22;
      display: flex;
      justify-content: center;
      align-items: center;
      color: white;
      font-size: 2em;
      animation-name: translate;
      animation-duration: 0.5s;
    }
    main {
      background: radial-gradient(at center, #e67e22, #e74c3c);
      display: flex;
      flex-direction: column;
      justify-content: center;
      align-items: center;
      animation-name: rotate;
      animation-duration: .5s;
      animation-delay: 2s;
      animation-fill-mode: backwards;
    }
    footer {
      background: #34495e;
      display:flex;
      justify-content: center;
      align-items: center;
      color: white;
      font-size: 2em;
      animation-name: rotate;
      animation-duration: .5s;
      animation-delay: 0.8s;
      
      /* transform: scale(0);
      animation-fill-mode: forwards; */

      /* 动画没动使用起始帧 */
      animation-fill-mode: backwards; 
    }
    div {
      width: 80vw;
      border-radius: 10px;
      opacity: .8;
      color: white;
      padding: 10px;
      box-shadow: 0 0 10px rgba(0, 0, 0, .8);
    }
    div:nth-child(1) {
      background: #8e44ad;
      transform: translateY(-40px);
    }
    div:nth-child(2) {
      background: #e74c3c;
    }
    @keyframes translate {
      from {
        transform: translateX(-100vw);
      }
      to {
        transform: translateX(0);
      }
    }
    @keyframes rotate {
      from {
        transform: scale(0) rotate(360deg);
      }
      to {
        transform: scale(1) rotate(0);
      }
    }
    @keyframes opacity {
      from {
        opacity: 0;
      }
      to {
        opacity: 1;
      }
    }
    .opacity {
      animation-name: opacity;
      animation-duration: .5s;
      animation-fill-mode: backwards;
    }
    .s3 {
      animation-delay: 3s;
    }
    .s4 {
      animation-delay: 4s;
    }
  </style>
</head>
<body>
  <header>header</header>
  <main>
    <div class="opacity s3">animation-name: none
      animation-duration: 0s
      animation-timing-function: ease
      animation-delay: 0s
      animation-iteration-count: 1
      animation-direction: normal
      animation-fill-mode: none
      animation-play-state: running</div>
    <div class="opacity s4">animation-name: none
      animation-duration: 0s
      animation-timing-function: ease
      animation-delay: 0s
      animation-iteration-count: 1
      animation-direction: normal
      animation-fill-mode: none
      animation-play-state: running</div>
  </main>
  <footer>footer</footer>
</body>
</html>